Method for achromatizing dye, device which uses the same, and method for recycling recording medium

ABSTRACT

The present invention provides a method for easily and quickly erasing images, including letters, formed on a printed matter at a low cost, and a device for utilizing the method. The images, including letters, on the printed matter are erased by bringing an oxidative gas generated by a remote plasma device into contact with a portion of the image, colored with a dye.

This application is a continuation of International Application No.PCT/JP2006/320034, filed on Sep. 29, 2006, which claims the benefit ofJapanese Patent Application No. 2005-289107 filed on Sep. 30, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for achromatizing a dye on aprinted matter to erase images, including letters, formed on the printedmatter, and a device which uses the method.

2. Description of the Related Art

Printing images on paper has been increasingly demanded as computers,printers, copiers and facsimiles are spreading. Demands for paper havebeen still increasing even now witnessing rapid development ofcomputerization and paperless systems, because no medium which exceedspaper in visibility and portability has been developed so far.

On the other hand, technological developments for recycling/reutilizingpaper are still gaining importance to effectively utilize limitedresources. The conventional paper recycling process involvesredeflocculation of recovered paper with water, removal of ink byfloatation in a deinking step, and bleaching. This method, however,involves problems of reduced paper strength and higher cost than thatfor producing new paper. Therefore, there are demands for paperreutilization or recycling methods which need no redeflocculation ordeinking step.

Under these situations, studies have been made recently on printingpaper with an image-forming material containing an erasable dyecomposition whose chromatic compound can be changed from color-developedstate to color-erased state. As such image-forming materials, JapanesePatent Application Laid-Open No. S63-039377 reports a material whichutilizes a reversible transparency change of a recorded layer caused bycontrolling thermal energy to be applied. Japanese Patent ApplicationLaid-Open No. 2001-105741 reports a material which utilizesintermolecular interactions between an electron-donating color fixingagent and electron-accepting color developing agent. Japanese PatentApplication Laid-Open No. H11-116864 discloses an ink containing a dyewhich loses its color when irradiated with electron beams, and JapanesePatent Application Laid-Open No. 2001-049157 discloses an ink containingan additive which can function to erase color of a colorant when it isirradiated with light. Moreover, the International Publication No.WO02/088265 pamphlet reports an ink jet ink erasable when irradiatedwith light by use of monascus dyes and a recording method using the ink.Japanese Patent Application Laid-Open No. H07-253736 proposes a methodwhich breaks and erases images recorded on ordinary paper in thepresence of an activated gas.

SUMMARY OF THE INVENTION

However, the methods disclosed by Japanese Patent Application Laid-OpenNos. S63-039377 and 2001-105741 are not practical, because of highinitial and running costs of recording media and writing/erasing deviceswhich they use. The method disclosed by Japanese Patent ApplicationLaid-Open No. H11-116864, which involves electron beam irradiation, maydeteriorate a medium base and generate a secondary X-ray, although to alimited extent. The ink disclosed by Japanese Patent ApplicationLaid-Open No. 2001-049157 is incorporated with an additive, which isspecifically a dye-based sensitizer, in a high 1/10 to 10/10 ratio byweight to a colorant to increase the ink cost. The methods disclosed bythe International Publication WO2002/088265 pamphlet and Japanese PatentApplication Laid-Open No. H07-253736 are required to erase images moreeasily and quickly.

It is an object of the present invention to easily and quicklyachromatize images, including letters, formed on a recording mediumrepresented by paper, more specifically to provide a method and a devicetherefor which can quickly achromatize a colored portion in which acolorant component (dye) of an ink is attached to or fixed on a printedmatter, to allow for recycling the recording media at a low cost forresource reutilization. It is another object to provide a method and adevice therefor which can achromatize a dye for recycling recordingmedia on which images are formed with the dye without causingdeterioration of their mechanical strength.

The inventors of the present invention have extensively studied toachieve the above objects by focusing on remote plasma dischargingtechniques carried out at the atmospheric pressure, which have beenemployed to treat exhaust gases or remove/decompose organiccontaminants. The conventional plasma treatment exposes a solid surfaceto a plasma in a plasma area (plasma space) or an area which issubstantially in contact with the plasma area. As a result, it producesozone at a very high concentration, several hundreds ppm or more.Therefore, it fails to efficiently achromatize a dye, one reasontherefor being a high load required to treat ozone.

The inventors of the present invention have found that a colored portionon a printed matter can be efficiently achromatized by exposing theportion to an oxidative gas generated by a remote plasma device, tooxidize the dye molecules which constitute the colored portion andadequately accelerate cleavage of the chemical bonds in the molecules.They have also found that achromatization of colored portion on printedmatter can be achieved by use of a remote plasma device whilecontrolling adverse effects on environments, that it can be achievedmore easily and quickly at a reduced cost by use of creeping, coplanaror dielectric barrier discharge as a plasma source, and that it can beachieved more efficiently when a porous inorganic pigment is present ona recording medium. It is also found that ionization potential of a dyein ink can be kept lower than that of the solid state when the ink isapplied to a recording medium coated with a porous inorganic pigment ofspecific properties, and that the above effect can be remarkablyenhanced when dye powder has a specific ionization potential beforebeing contained in an ink and exhibits a specific ionization potentialrelative to that of the solid dye after being applied to a recordingmedium. The present invention has been developed, based on thesefindings.

More specifically, one aspect of the present invention is a method forachromatizing a dye on a printed matter, comprising exposing the dye toan oxidative gas generated by a remote plasma device.

Another aspect of the present invention is a device for achromatizing adye on a printed matter, comprising a remote plasma device whichproduces an oxidative gas by using any discharging means of coronadischarge, creeping discharge and dielectric barrier discharge, andsupporting means for positioning the printed matter in such a way thatthe dye thereon is exposed to the oxidative gas.

Still another aspect of the present invention is a method for recyclingrecording media, comprising a step for achromatizing a colored portionon a printed matter by the above achromatizing method.

The method for achromatizing a colored portion on a printed matter andthe device therefor, both of the present invention, can easily andquickly erase images on a recording medium represented by paper.Moreover, they can quickly and easily achromatize a colored portionwhile controlling deterioration of mechanical strength of the recordingmedium for the printed matter, and allow for recycling of the recordingmedium at a reduced cost. The present invention can reutilize usedrecording media as resources.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view schematically illustrating one embodiment of theachromatization device of the present invention.

FIG. 2A is a side view schematically illustrating another embodiment ofthe achromatization device of the present invention.

FIG. 2B is a side view schematically illustrating a remote plasma devicefor the device shown in FIG. 2A.

FIG. 3 is a side view schematically illustrating still anotherembodiment of the achromatization device of the present invention.

FIG. 4 is a side view schematically illustrating still anotherembodiment of the achromatization device of the present invention.

FIG. 5 schematically illustrates one embodiment of power source for theachromatization device of the present invention.

FIG. 6 schematically illustrates one embodiment of an aerial gap for theachromatization device of the present invention.

FIG. 7 schematically illustrates one embodiment of an aerial gap for theachromatization device of the present invention.

DESCRIPTION OF THE EMBODIMENTS

The method of the present invention for achromatizing a dye on a printedmatter comprises at least one step of exposing the dye which constitutesa colored portion on the printed matter to an oxidative gas generated bya remote plasma device.

The term “achromatization” used in this specification means to reduceoptical density of images, including letters, on a printed matter to asufficient level to allow the recording medium to be recyclable. Itincludes not only a case where a portion colored with an ink on arecording medium is completely invisible (“erased” in this case) butalso a case where the portion loses optical density by 80% or less ofthe initial level (“reduced color” in this case). In terms of residualoptical density rate, the “reduced color” means that a colored portionhas an optical reflectivity of 20% or less of the initial level at themaximum absorption wavelength.

<Recording Medium>

The recording media to which the achromatization method of the presentinvention is applicable are not limited so long as they can be printedwith an erasable ink. They include paper, films, photographic paper,seals, labels, compact disks, IC cards, various tugs, metals, glass,various plastic products, slips, e.g., those for home delivery systems,and a combination thereof. Paper may be acidic, neutral or alkaline solong as it is recyclable. The paper may be produced by a commonpaper-making method which mainly uses chemical pulp (represented by LBKPor NBKP) and a filler, and may use an internal sizing agent orpaper-making aid, as required. The pulp material to be used may be amaterial which uses a combination of mechanical pulp and recycled pulp,or a material mainly composed thereof. The fillers include calciumcarbonate, kaolin, talc and titanium dioxide. The paper thus producedmay be incorporated with, or coated with, a hydrophilic binder, mattingagent, film curing agent, surfactant, or polymer latex or dye mordant.The paper preferably weighs in a range from 40 to 700 g/m².

The recording media to which the achromatization method of the presentinvention is applied preferably have a porous inorganic pigment on thesurface, and are preferably coated with a layer containing an inorganicpigment. The porous inorganic pigment may have a spherical or irregularshape. It preferably has a pore volume of 0.2 cc/g or more and 2.0 cc/gor less, and dispersed particle diameter of 0.01 μm or more and 0.5 μmor less. It preferably satisfies these two conditions simultaneously.When an ink containing the porous inorganic pigment having a pore volumeand/or dispersed particle diameter in the above range is fixed on arecording medium, the dye exhibits an ionization potential lower thanthat of the solid state by 0.1 eV or more. As a result, it can realizean excellent ink achromatization effect. The pore volume of the porousinorganic pigment may be determined by a mercury porosimeter whichpenetrates mercury into the sample. The pore volume of the porousinorganic pigment alone can be determined from a pore volumedistribution against a pore diameter, measured by the mercurypenetration, because a recording medium and an inorganic pigmentgenerally have a different pore diameter. The dispersed particlediameter may be determined by scanning electron microscopy.

The porous inorganic pigments include alumina, silica, silica-alumina,colloidal silica, zeolite, clay, kaolin, talc, calcium carbonate, bariumsulfate, aluminum hydroxide, titanium dioxide, zinc oxide, satin white,diatomaceous earth, acid clay, and a composite of alumina or silica.

A recording medium with a porous inorganic pigment may be produced bycoating a recording medium of paper (base paper) with an aqueous coatingsolution prepared by incorporating the porous inorganic pigment with anaqueous binder. The aqueous binders useful for the present inventioninclude, but not limited to, the following water-solublehigh-molecular-weight compounds, e.g., polyvinyl alcohol, casein,styrene/butadiene rubber, starch, polyacrylamide, polyvinyl pyrrolidone,polyvinyl methyl ether and polyethylene oxide.

The porous inorganic pigment/aqueous binder mass ratio is in a rangefrom 0.1 to 100, preferably 1 to 20. When the mass ratio is 100 or less,exfoliation of the porous inorganic pigment from the recording medium, aso-called powder dropping can be prevented. When it is 0.1 or more, theexcellent color reduction or erasion effect of ink jet images formed onthe recording medium can be realized. The aqueous coating solution maybe incorporated with a pigment dispersant, water retention agent,thickening agent, defoaming agent, releasing agent, colorant, waterresistant agent, wetting agent, fluorescent dye or UV absorber, asrequired.

A recording medium may be coated with an aqueous coating solution byroll coating, blade coating, air-knife coating, gate roll coating, barcoating, spray coating, gravure coating, curtain coating or commacoating.

A recording medium is preferably coated with an aqueous coating solutionto 0.1 to 50 g/m² as solids. At 0.1 g/m² or more, color reduction orerasion of ink jet images on the recording medium can be quicklyperformed. At 50 g/m² or less, on the other hand, wasteful aqueouscoating solution consumption can be avoided.

A recording medium coated with an aqueous coating solution may befurther coated with an aqueous solution containing nitrate, sulfate,formate or acetate of zinc, calcium, barium, magnesium or aluminum whilethe coating solution is still wet, prior to the subsequent step. Thistreatment will help solidify the aqueous binder in the solution. Therecording medium having the surface treated can be produced by dryingthe recording medium coated with the aqueous coating solution by a hotwind drying furnace or heat drum. When the coating film of the aqueouscoating solution on the recording medium is dried by a heat drum, acoated layer can be obtained by pressing the heated coating film to thedrum before drying. After drying, a strong coating film without filmexfoliation or powder dropping can be obtained by subjecting therecording medium to a calendar treatment.

<Ink>

The mechanisms of the achromatization for the present invention toreduce or erase color of a dye, which constitutes a colored portion on aprinted matter conceivably, result from cleavage of the dye chemicalbonds, accelerated when they are exposed to an oxidative gas. The dyeachromatization can easily proceed when a solid dye has an ionizationpotential of 6.0 eV or less. Moreover, it is essential for a solid dyeto have an ionization potential of 4.2 eV or more, in order to preventoxidation and light-caused deterioration in air.

It is also necessary for a dye held on a recording medium to have anionization potential lower than that of the solid state by 0.1 eV ormore, specifically by 0.15 to 0.7 eV or less. A dye having the aboveionization potential relationship after the ink is applied to arecording medium can be easily and quickly achromatized. It is alsonecessary that the porous inorganic pigment has a pore volume of 0.2cc/g or more and 2.0 cc/g or less or a dispersed particle diameter of0.01 μm or more and 0.5 μm or less, in order to keep the ionizationpotential of the dye in the ink applied to the recording medium in theabove range.

The mechanisms are considered to take place by the following phenomena,although not fully substantiated.

It is known that the value of ionization potential of a dye is closelyrelated to the agglomerated conditions of dye molecules (T. Ma, K.Inoue, H. Noma, K. Yao and E. Abe, Ionization potential studies oforganic dye absorbed onto TiO₂ electrode, Journal of Materials ScienceLetters, 2002, vol. 21, p. 1013 to 1014). When a dye-containing ink isapplied to a recording medium containing a porous inorganic pigment, onthe other hand, the dye molecules are adsorbed on the surface pores ofthe porous inorganic pigment to control agglomeration of the dyemolecules with each other. As a result, the dye tends to have anionization potential lower than that of the solid state (agglomeratedstate). It is therefore essential to select a porous inorganic pigmenthaving an adequate pore volume or dispersed particle diameter for dyemolecules contained in an ink to reduce ionization potential of the dyein the ink applied to a recording medium.

Such a value of dye ionization potential can be determined by an aerialphotoelectron spectrometer (e.g., AC-1, Riken Keiki) at a contact pointbetween photoelectron emitting current and photon energy which followsFowler's rule.

The ink for producing a printed matter to which the achromatizationmethod of the present invention is applicable is not limited, so long asit contains an erasable dye which can be fixed on a recording medium.Images can be formed on a recording medium by any printing method whichuses an ink jet printer, copier, printer or the like. It may be used forforming images by a utensil, represented by pen, but is preferably usedfor ink jet printing. Examples of the inks useful for the presentinvention include those containing a dye dissolved, dispersed ordissolved and dispersed in an organic solvent or water.

(Dye)

The erasable dye is not limited. For example, it may be natural orsynthetic, or any dye which can develop color in the presence of adeveloping agent. However, it preferably has a polyene structure.Conjugated carotenoid polyenes, represented by annatto and gardeniayellow dyes, can be cited as dyes of polyene structure. The erasable dyemay be natural or synthetic, the former being more preferable inconsideration of the effects on human bodies. Microbial dyes produced bymicroorganisms and dyes extracted from animals or plants can be cited asexamples of natural dyes. Microbial dyes are produced by an easierproduction management procedure, more stably and more massively thanextracted ones.

Microbial dyes are produced from strains capable of producing the dyesby unlimited known culturing methods. They are generally extracted froma culture solution of the microorganisms. The culture solution may bedirectly incorporated in an ink after being concentrated without beingtreated for extraction or refining, so long as it can retain inkcharacteristics. Specific examples of these microbial dyes includemonascus, violacein, melanin, carotenoid, chlorophyll, phycobilin,flavin, phenajine, prodigiosin, violacein, indigo, benzoquinone,naphthoquinone and anthraquinone dyes, and other known ones (Dyemicrobiology, P. Z. Margalith, Chapman & Hall, London, 1992). Of thesedyes, those exhibiting excellent erasability with an acidic gas,described later, are monascus, anthraquinone, violacein and indigo ones,especially monascus dyes.

Monascus dyes are those produced by filamentous bacteria belonging togenus Monascus (monascus bacterium), and have been used as colorants forred wines and meats in China and Taiwan for long years. Therefore, theirsafety has been confirmed. Monascus dyes are generally compositions ofcompounds of similar structure with different substituents, e.g.,monascorubrin for orange color; ankaflavin and monascin for yellowcolor; and monascorubramin for red color, rubropunctatin andrubropunctamine (J. Ferment., Technol., Vol. 51, p. 407, 1973). They areinsoluble in water, but monascorubrin and rubropunctatin are known tomake water-soluble red monascus dyes when treated with a water-solubleamino compound, e.g., water-soluble protein, peptide or amino acid in aculture solution to produce a water-soluble complex (Journal ofIndustrial Microbiology, Vol. 16, pp. 163 to 170, 1996).

The strain for producing a monascus dye is not limited so long as it isa filamentous bacterium belonging to genus Monascus. These filamentousbacteria include Monascus purpureus (catalog No. NBRC 4478, IncorporatedAdministrative Agency National Institute of Technology and EvaluationBiological Resource Center (NBRC)), Monascus pilosus (NBRC 4480) andMonascus ruber (NBRC 9203). Their variants and mutant strains are alsoincluded.

A strain for producing a monascus dye may be cultured in a solid orliquid medium, the former producing a monascus dye powder and the lattera liquid monascus dye or its extract with an organic solvent. Theculture medium may be a known one containing a carbon source, nitrogensource, inorganic salt and trace quantities of nutrient(s). The carbonsources include saccharides, e.g., glucose or sucrose, acetic acid andhydrolyzed starch. The nitrogen sources and trace quantities ofnutrients include peptone, yeast extract and malt extract. The inorganicsalts include sulfates and phosphates.

More specifically, a monascus strain can be produced by culturing thebacterium inoculated in a medium, at 20 to 40° C. in an aerobicatmosphere for 2 to 14 days. The culture system needs no pH control whenstirred by aeration. A dye, which contains monascorubrin andrubropunctatin at a high concentration, can be produced under an acidiccondition, because of controlled reactions of monascorubrin andrubropunctatin with water-soluble amino acid (Journal of IndustrialMicrobiology, Vol. 16, pp. 163 to 170, 1996).

A monascus dye can be extracted from the culture solution or bacteriafraction with an organic solvent. The supernatant culture solution maybe directly used as the dye after being solidified. The usefulextractants include n-propyl alcohol, methanol, ethanol, butanol,acetone, ethyl acetate, dioxane and chloroform. For refining theextract, it may be isolated by a common isolation technique, e.g.,silica gel chromatography or reverse-phase, high-speed liquidchromatography. It can be refined to produce a monascus dye of desiredpurity.

The monascus dye thus produced is a mixture of water-insoluble andwater-soluble components, the former including monascorubrin,rubropunctatin, ankaflavin, monascin, monascorubramin, andrubropunctamine, and the latter including monascorubrin orrubropunctatin bound to an water-soluble amino compound in the culturingstep.

When the cultured monascus dye is incorporated in the ink of the presentinvention, the supernatant culture solution or its extract may bedirectly used, as discussed above. However, it is preferably treatedwith a water-soluble amino compound before being incorporated in theink, because of accelerated production of a water-soluble complex ofmonascorubrin or rubropunctatin with the water-soluble amino compound.This procedure increases a water-soluble component content in the dyeand thereby to improve color reduction or erasion capacity of the inkfor the present invention.

The water-soluble component content in the dye can be increased by thefollowing procedure which incorporates a water-soluble amino compound inthe cultured monascus dye. First, a monascus bacterium is cultured underan acidic atmosphere with acetic acid as a pH adjuster being supplied tothe medium. The culture under an acidic atmosphere produces a dyemassively containing water-insoluble monascorubrin or rubropunctatinwhile controlling its reactions with a water-soluble amino compound.Then, the culture solution is incorporated with an excessive quantity ofa water-soluble amino compound and treated by centrifugal separation orfiltration, after being adjusted at a neutral pH level, to recover thebacterium. This produces a dye of increased water-soluble componentcontent. Alternately, the solution which cultures the bacterium under anacidic atmosphere may be treated with an organic solvent to extract adye containing monascorubrin or rubropunctatin, and the extract isreacted with a water-soluble amino compound. This produces a monascusdye of decreased impurity component, as a mixture of limited number ofdyes. When applied to the achromatization method of the presentinvention, it can improve color reduction or erasion capacity of theink. The extractants useful for recovering the dye from the culturesolution include ethyl acetate, acetone, butanol, ethanol and methanol.Of these extractants, ethyl acetate improves the achromatization effectof the present invention, when the extract is washed with water.

The water-soluble amino compound to be incorporated in the culturedmonascus dye is at least one selected from the group consisting of aminoacid, water-soluble protein, peptide and nucleic acid compound, or amixture thereof. Such an amino compound can provide the presentinvention with an excellent color erasion effect. When the dye isincorporated with a water-soluble amino compound, after being extracted,the extractant is not limited. However, it is recommended to use a 50%by mass aqueous solution of ethanol, methanol or acetonitrile.

Violacein as a natural dye is a microorganism belonging to genusChromobacterium, Janthinobacterium or Alteromonas. Those having avariant or mutant strain of the above bacterium are also useful.

Violacein may be produced by use of Janthinobacterium lividum (Instituteof Physical and Chemical Research's catalog no. JCM9045). It gives abluish purple dye in a greatly varying yield depending on type ofculture medium used. It is recommended that the bacterium is cultured ina medium which gives the dye in a high yield, e.g., that of mannitol YEor semi-synthetic potato, at 5 to 30° C. and pH 6.0 to 8.0. The dye canbe extracted from the bacterium with a solvent. The useful extractantsinclude n-propyl alcohol, methanol, ethanol, dioxane and chloroform. Forrefining the extract, it may be isolated by a common isolationtechnique, e.g., silica gel chromatography or reverse-phase, high-speedliquid chromatography. It can be refined to produce violacein of desiredpurity. Moreover, the extract may be directly used, after beingconcentrated.

The extracted natural dye for the present invention is not limited. Someexamples include those extracted from plants, e.g., tumeric, gardenia,carotin, safflower, annatto, capsicum, Japanese basil, grape juice, redradish, red cabbage, purple sweet potato, chlorophyll, cacao and indigodye plants; and from animals, e.g., lac, cochineal and sepia. Of these,those from gardenia and capsicum give a higher color erasion effect. Thesynthetic dye useful for the ink for the present invention is notlimited. Some examples include those based on anthraquinone,triphenylmethane, phthalocyanine, polyene and indigo.

(Solvent)

The organic solvent working as a liquid medium component to dissolve ordisperse a dye for the ink may include organic solvents used for an inkjet ink. More specifically, these solvents include alcohol, glycol,glycol ether, fatty acid ester, ketone, ether, hydrocarbon solvent andpolar solvent. Of these, those working as good organic solvents fordissolving or dispersing the above dyes include alcohols, e.g.,methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol,isobutyl alcohol or t-butyl alcohol; and glycols, e.g., ethylene glycol,diethylene glycol, triethylene glycol, polyethylene glycol, propyleneglycol, dipropylene glycol, polypropylene glycol, butylenes glycol,hexane diol, pentane diol, glycerin, hexane triol and thiodiglycol.

These organic solvents may be used alone or in combination of two ormore. Specific examples of the combinations include an alcohol and polarsolvent, glycol and polar solvent, and alcohol, glycol and polarsolvent. The polar solvents useful for the present invention include2-pyrrolidone, formamide, N,N-dimethylformamide, N,N-dimethylacetoamide,dimethylsuloxide, sulfolane, N-methyl-2-pyrrolidone,N-vinyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone,acetonitrile and acetone.

The organic solvent may be incorporated with water, when it is solublein water. In this case, water is incorporated at 30 to 95% by mass basedon the whole ink composition.

A dye, which can be achromatized, may be dispersed or dissolved in thesolvent by merely incorporating the dye in the solvent. Alternately, adye is dispersed in the presence of dispersant (surfactant) after beingfinely divided by a dispersing machine. Dispersing machines include ballmill, sand mill, attritor, roll mill, agitator mill, Henschel mixer,colloid mill, supersonic homogenizer, pearl mill, jet mill and angmill.

The surfactant for the present invention may be anionic, cationic,amphoteric or nonionic.

The dye is incorporated in the ink at 0.01% by mass or more and 90% bymass or less based on the whole ink composition, preferably 0.5% by massor more and 15% by mass or less. The ink containing the dye at thecontent in the above range can form good images on a recording medium.The ink may be incorporated with a binder, pH adjustor, viscosityadjustor, penetrating agent, surface tension adjustor, oxidationinhibitor, preservative or antifungal agent.

<Achromatization of Colored Portion on Printed Matter>

The achromatization method of the present invention exposes a coloredportion on a printed matter to a plasma generated by discharging ofvarying type and an oxidative gas as a secondary product of dischargingto achromatize a dye which constitutes the colored portion. It is anessential characteristic of the present invention to treat a surface tobe treated of a printed matter having a colored portion spaced from theplasma region. This essentially differentiates the present inventionfrom the conventional plasma treatment which exposes a varying solidsurface to a plasma in the plasma region (plasma space) or in an areasubstantially in contact with the plasma region. The present inventiondoes not directly expose a printed matter to a plasma, and brings itinto contact with an oxidative gas without being affected by the plasmaregion. In short, it allows the oxidative gas generated in the plasmaregion to exhibit its positive or selective functions by introducing thegas in the contact region while controlling the direct effects ofcharging species, e.g., ion species or electrons, present in the plasmaregion on the contact region with the printed matter.

As discussed above, the present invention, unlike the conventionalplasma treatment, actively utilizes an acidic gas generated by a plasmafor surface treatment. In order to selectively utilize the oxidative gasafter separating it from the other ion species and electrons, thesurface to be treated is spaced from the plasma region. The surfacetreatment with the surface spaced from the plasma region is referred toas “remote plasma treatment” in this specification.

In the present invention, a remote plasma device is supplied with areactive gas from the outside to generate a plasma, by which anoxidative gas is generated. At least one species selected from ozone,hydroxyl radical, carbonate ion and nitrogen oxide present in theoxidative gas generated in the plasma region is actively involved in thedye achromatization. This promotes the chemical reactions for theachromatization. The oxidative gas, represented by ozone, is mostlyutilized for the achromatization of a colored portion on a printedmatter, and it is possible to keep production of the oxidative gas,represented by ozone, at a necessity minimum level. The presentinvention, which treats a surface to be treated of a printed matterspaced from the plasma region as the essential characteristic, issuitable for achromatization of printed matter incorporated inelectronic devices, represented by IC cards and IC tags.

Means for generating a plasma for the present invention may be selectedfrom known ones, preferably from those for generating discharge plasmaby corona discharge, creeping discharge, coplanar discharge ordielectric barrier discharge. It is equipped with means for introducinga reactive gas, e.g., air, oxygen, nitrogen, carbon dioxide, steam or acombination of two or more thereof.

<Device for Achromatizing Colored Portion on Printed Matter>

The dye achromatization device of the present invention exposes acolored portion on a printed matter to an oxidative gas generated by aremote plasma device to achromatize the colored portion. Preferabledischarging means for generating an oxidative gas include thoseproducing corona discharge, creeping discharge or dielectric barrierdischarge. The achromatization device of the present invention is alsoequipped with means for supporting a printed matter with which anoxidative gas generated by the remote plasma device is brought intocontact. The achromatization device of the present invention isdescribed by referring to the attached drawings, where air is used as areactive gas.

Corona discharge is generated by applying a voltage between a dischargeelectrode and opposing counter electrode to generate an oxidative gas.The voltage to be applied to the discharge electrode may be direct oralternating.

FIG. 1 is a side view schematically illustrating one embodiment of theachromatization device of the present invention, where images (includingletters) on a printed matter formed on a recording medium by ink jetrecording are achromatized by a remote plasma device which uses coronadischarge. Corona discharge is generally generated by applying a voltagebetween a discharge electrode and an opposing counter electrode.

The device shown in FIG. 1 has a discharge electrode 41 and anelectroconductive metallic plate 42 as a counter electrode, the formerhaving needle shapes on one side. It is recommended to ground theelectroconductive metallic plate 42, as shown in FIG. 1, to efficientlygenerate an ionized/dissociated gas and its secondary products. In FIG.1, reference numeral 3 is DC voltage applying means, and referencenumeral 4 is a remote plasma device with the plate-shape dischargeelectrode 41 and the counter electrode 42. The voltage may be of DC orAC superimposed on DC. Applying a DC voltage of negative polarity on thedischarge electrode 41 efficiently helps erase images, conceivablybecause it efficiently generates a dissociated gaseous compositioncomprising an ionized/dissociated gas of oxidative gas and its secondaryproduct, effective for achromatizing a dye which constitutes a coloredportion.

The discharge electrode 41 and the counter electrode 42 may be made of ametal, e.g., Al, Cr, Au, Ni, Ti, W, Te, Mo, Fe, Co, and Pt, or an alloyor oxide thereof. Corona discharge can be initiated by applying avoltage of a predetermined threshold level (discharge initiationvoltage) or more.

The DC voltage to be applied to the discharge electrode for the presentinvention is preferably in a range from −0.5 to −20 kV, more preferablyfrom −0.5 to −10 kV for more efficient image achromatization.

The image color reduction/erasion is effected in the following manner.First, a reactive gas is introduced into the remote plasma device, whereit is sent by a fan (not shown) from backward of the device. The“backward” means an opening located opposite to the port through whichan oxidative gas is sprayed, shown in FIG. 1. The reactive gas introducebecomes an oxidative gas in the space between the discharge and counterelectrodes. The oxidative gas is sprayed onto a running or stationaryprinted matter at a rate corresponding to that of the reactive gas. Thereactive gas and oxidative gas to be sprayed onto printed matterpreferably flow at 0.1 to 5 m/second.

In the present invention, the printed surface is preferably spaced fromthe plane (center) from which the gas is emitted in the remote plasmadevice by more than 0 and 100 mm or less. This distance will secureefficient achromatization. The distance is more preferably 5 mm or moreand 100 mm or less.

In the present invention, the means for supporting a printed matter mayinclude means for transferring the printed matter into or out of theregion in which it is exposed to the oxidative gas. The transferringmeans is at least one type selected from the group consisting of endlessbelt, roll and drum. It may run in a unidirectional or back and forthmanner or combination thereof. In this invention, a printed matter ispreferably stationary or moving at a relative velocity of 2000 cm/minuteor less to the plane from which an oxidative gas is emitted in a remoteplasma device, in order to efficiently achromatize a colored portion. Itis more preferable to move at 600 cm/minute or less, if it moves. In thecase where a stationary printed matter is exposed to an oxidative gas, aremote plasma device itself may be moved at the above velocity over theentire surface of the printed matter. The above preferable velocity isgiven by a relative velocity between the printed matter and remoteplasma device.

The discharge electrode 41 is not limited in shape; it may have a shapeof needle, roll, blade, plate, brush, wire or bar.

Creeping discharge is triggered by applying an AC voltage between a pairof electrodes spaced from each other via a dielectric, over whichdischarge creeps to generate an oxidative gas.

FIG. 2A is a side view schematically illustrating another embodiment ofthe achromatization device of the present invention, where images on aprinted matter are achromatized by a remote plasma device which usescreeping discharge. An oxidative gas generated by creeping dischargeoccurring in air comprises ionized/dissociated gas and its secondaryproduct, e.g., ozone, carbonate ion or nitrogen oxide. In FIG. 2A, adischarge electrode 41 for creeping discharge comprises a pair of adischarge electrode 41 and a counter electrode 42 which are separated bya dielectric 43 opposed to each other.

As illustrated in FIG. 2B, a remote plasma device 4 is cylindricalhaving an elliptical cross-section in the oxidation gas sprayingdirection, with the counter electrode 42 being embedded in thedielectric 43 and the discharge electrode 41 being provided on the innersurface of the dielectric 43. An oxidation gas is generated on the innersurface of the dielectric 43 near the discharge electrode 41.

In FIG. 2A, reference numeral 2 is an AC power source. The remote plasmadevice for generating creeping discharge is not limited in shape. Oneexample is shown in FIG. 3, which illustrates a structure for generatingdischarge commonly referred to as coplanar discharge having awire-shaped discharge electrode 41 and counter electrode 42, the formerbeing embedded in a dielectric 43. The electrodes 41 and 42 may be madeof a material selected from those used for generating corona discharge,described before. The dielectric 43 is made of a material which canprovide a surface on which creeping discharge occurs. Some of theexamples include ceramics and glass, e.g., metal oxides represented bysilica, magnesia and alumina; and nitrides represented by siliconnitride and aluminum nitride.

The discharge electrode 41 and the counter electrode 42 are spaced fromeach other preferably by 1 μm or more, more preferably 3 to 200 μm. AnAC voltage (Vpp) to be applied to the discharge electrode 41 ispreferably in a range from 1 to 20 kV, and preferably has a frequency of100 Hz to 5 MHz. The combination of the above voltage and frequency canmore efficiently generate an oxidative gas. A combination of Vpp of 1 to10 kV and frequency of 1 kHz to 2 MHz is more preferable.

The image color reduction/erasion with an oxidative gas generated bycreep discharge is effected in a manner similar to that for the coronadischarge case. A reactive gas is introduced from backward of the remoteplasma device 4, and the oxidative gas produced in the discharge spacebetween the discharge electrode and the counter electrode is sprayedonto a running or stationary printed matter.

The achromatization conditions in this case are similar to those in thecorona discharge case with respect to the preferable ranges of rate ofthe reactive gas to be introduced and the oxidative gas to be sprayed,distance between the printed surface and the plane (center) from whichthe oxidative gas is emitted, and rate at which a printed matter istransferred while being exposed to an oxidative gas.

Dielectric barrier discharge is generated by applying a voltage betweena pair of electrodes coated with a dielectric on the inner side of atleast one of the electrodes, to generate a plasma of a gas present inthe space between the electrodes. It can stably generate a plasma underan atmospheric pressure. Corona discharge and creeping dischargedescribed above can generate an oxidative gas. However, adoption ofbarrier discharge more improves generation efficiency of an oxidativegas.

FIG. 4 is a side view schematically illustrating one embodiment of theachromatization device of the present invention, where images on aprinted matter are achromatized by a remote plasma device which usesdielectric barrier discharge. In FIG. 4, a pair of opposing electrodes,discharge electrode 41 and counter electrode 42 for barrier dischargeare spaced from each other via a dielectric 43. As shown in FIG. 4, theremote plasma device 4 is plate-shaped, and generates an oxidative gasin the vicinity of the dielectric 43 and counter electrode 42, when avoltage is applied between the dielectric-coated discharge electrode 41and the counter electrode spaced from the discharge electrode 41.

A voltage (Vpp) to be applied between the discharge electrode 41 and thecounter electrode 42 is preferably in a range from 1 to 40 kV, andpreferably has a frequency of 10 Hz to 20 kHz. The combination of theabove voltage and frequency can more efficiently generate an oxidativegas. A combination of Vpp of 1 to 30 kV and frequency of 20 Hz to 10 kHzis more preferable. The AC voltage to be applied may have a sinusoidal,triangular, square or pulsed waveform, or a combination thereof.

The power source for barrier discharge is not limited, so long as it canproduce an AC voltage having a Vpp level of 1 to 40 kV and frequency of10 Hz to 20 kHz. However, a commercial AC power source which uses asemiconductor is expensive. On the other hand, a power source which usesan aerial gap can decrease the power source cost to one-tenth or lessthat of the above source. FIG. 5 schematically illustrates oneembodiment of power source for the achromatization device of the presentinvention which generates barrier discharge. It has a simple structurewith a commercial transformer 71 as an input power source, electricelements 72 to 75 and an aerial gap 8 connected to each other. Each ofthe electric elements 72 and 73 is a resistor or coil, and the electricelements 74 and 75 are a capacitance and a resistor, respectively. Theaerial gap 8 is composed of a combination of any of needle, flat plate,blade and cylinder. The gap material is not limited, so long as it iselectroconductive.

FIG. 6 and FIG. 7 schematically illustrate one embodiment of an aerialgap for the achromatization device of the present invention. Each hasplate-shape metallic electrodes 81 and 82 of different size, rotating inthe opposite direction to reduce effects of aerial discharge, which maydeteriorate the gap. An AC voltage having a Vpp of 1 to 40 kV andfrequency of 10 Hz to 20 kHz, including a pulsed waveform, can begenerated to secure good barrier discharge by applying an AC voltage ofcommercial frequency to a transformer 71 and keeping the aerial gap 8between the plate-shaped metallic electrodes at any value of 10 mm orless. The gap distance, and type and size of the electric elements canbe optionally selected in accordance with shape and size of the barrierdischarge electrode.

The dielectric barrier discharge electrode may be made of a metal; e.g.,Sn, In, Al, Cr, Au, Ni, Ti, W, Te, Mo, Fe, Co, and Pt or an alloythereof; oxide, e.g., ITO or ZnO; or polymer sheet or rubber beltdispersed with electroconductive particles. Its shape may be plate,mesh, belt, drum or linear. The electrodes may have a different shape.

The dielectric 43 which coats the electrode is made of a dischargingmaterial, e.g., carbon compound, ceramic, glass, ferroelectric materialor polymer. More specifically, the dielectric materials include diamondand diamond-like carbon; metal oxides represented by silica, magnesia,alumina and zirconia; nitrides represented by silicon nitride andaluminum nitride; and magnesium titanate, barium titanate, leadzirconate titanate, polyethylene, vinyl chloride, polyethyleneterephthalate, acryl, polycarbonate and polyvinylidene fluoride.

The dielectric can be applied in such a manner that the above materialmay be put on the electrode after being formed into a sheet, or may becoated with an electrode layer by ion plating carried out under avacuum. Moreover, it may be applied in the form of composite composed ofthe above materials dispersed in a binder. The image colorreduction/erasion with an oxidative gas generated in the discharge spacebetween the discharge and counter electrodes is effected in a mannersimilar to that for the corona discharge case, where a reactive gas isintroduced from backward of the remote plasma device 4, and theoxidative gas produced by the device is sprayed onto a running orstationary printed matter.

The achromatization conditions in this case are similar to those in thecorona discharge case with respect to the preferable ranges of rate ofthe reactive gas to be introduced and the oxidative gas to be sprayed,distance between the printed surface and the plane (center) from whichthe oxidative gas is emitted in the remote plasma device, and rate atwhich a printed matter is transferred while being exposed to anoxidative gas.

<Time Required for Achromatization>

Images and letters formed by dye-containing colored portions on aprinted matter can be discolored (reduced in color) by exposing them toan oxidative gas, preferably to an invisible extent. In other words,color of a dye present on or near a printed matter surface becomesfaint, eventually to an invisible extent, by being exposed to anoxidative gas. Dye achromatization is greatly depends on dischargevoltage. However, time required for achromatization varies depending onvarious conditions, e.g., oxidative gas concentration, contactefficiency with an oxidative gas, rate and composition of an oxidativegas, type, concentration and composition of a dye, recording mediummaterial. Achromatization time can be controlled by selecting theseconditions. When dye concentration on a printed matter is determined bya line or image sensor prior to the achromatization treatment by aremote plasma device, time for which the printed matter is exposed to anoxidative gas can be varied depending on dye concentration, to achieveuniform achromatization at any concentration.

As discussed above, it is preferable to introduce a reactive gas frombackward of a remote plasma device at a rate of 0.1 to 5 m/second togenerate an oxidative gas in a discharge space between a dischargeelectrode and a counter electrode, and to spray the oxidative gas onto arunning or stationary printed matter. Exposure of a printed matter to anoxidative gas may be optionally achieved in a closed or open system,depending on a purpose. A close system is more preferable for thepresent invention to prevent leakage of the oxidative gas from thedevice. The system, whether it is closed or open, is preferably equippedwith an adsorption filter to prevent leakage of the oxidative gas.

When a printed matter is exposed to an oxidative gas in a closed system,a remote plasma device is preferably provided with a feedback mechanismto keep ozone concentration at a constant level. Ozone concentration canbe determined by UV absorptiometry in the remote plasma device bycomparing the gas with a reference gas. It is preferable to keep anozone concentration at 100 ppm or more in the device for theachromatization. It is also preferable to swiftly generate an oxidativegas by operating a discharger in the remote plasma device, when theozone concentration is below the above level.

On completion of the achromatization of a printed matter by the presentinvention, the discharger is preferably heated up by increasing voltageor frequency applied to the discharger to decompose ozone unnecessaryfor the achromatization. The atmosphere temperature is preferably keptat 100° C. or higher to efficiently decompose ozone.

<Method for Recycling Recording Medium>

The method of the present invention for recycling a recording mediumfrom a printed matter is not limited, so long as it comprises a step forthe achromatization of the present invention. It uses an oxidative gasto accelerate cleavage of a dye in an ink fixed on a printed matter, andcan efficiently, easily and quickly achromatize the dye on a printedmatter.

In the present invention, a printed matter is preferably kept at 20° C.or higher and 50% RH or more in a steam atmosphere before it is exposedto an oxidative gas generated by dielectric barrier discharge, becausethe steam treatment accelerates separation of the dye on the printedmatter in the form of monomolecular state and thereby to achromatize thedye more efficiently, easily and quickly.

Moreover, the present invention can leave no dye-oxidizing substance onthe recycled recording medium. Therefore, it allows the recycled mediumto be reused, because a dye in a fresh ink fixed on the achromatized dyecan retain its color without being cleaved.

EXAMPLES

The Present invention is described in more detail by EXAMPLES, which byno means limit the technical scope of the present invention.

Recording Medium Preparation Example 1

An 85/15 by mass mixture of fine alumina powder (Cataloid® AP-3,Catalyst and Chemical Ind.) and polyvinyl alcohol (SMR-10HH®, Shin-EtsuChemical) was prepared, and incorporated with water to have a solidcontent of 20% by mass and stirred. It was spread on a PET film to 30g/m² (dry basis), and dried at 110° C. for 10 minutes. The resultingrecording medium was named RECORDING MEDIUM 1.

Recording Medium Preparation Example 2

A 2 L stirrer-equipped flask was charged with the following components,which were stirred at room temperature for 30 minutes to prepare auniform mixture. It was heated at 80° C. for 2 hours and then cooled tohave a viscous, transparent liquid (BINDER A):

polyethylene glycol (average molecular weight: 2000), 800 g

hexamethylene diisocyanate, 65 g

dibutyl tin laurate, 2 g and

ethylene glycol dimethyl ether, 900 g.

The liquid prepared had a viscosity of 30,000 mPa·s at 25° C., and thepolymer in ethylene glycol dimethyl ether as a solvent had anumber-average molecular weight of 85,000.

Next, RECORDING MEDIUM 2 was prepared in the same manner as in RECORDINGMEDIUM PREPARATION EXAMPLE 1, except that polyvinyl alcohol was used asBINDER A obtained in the above procedure.

Recording Medium Preparation Example 3

A 2 L stirrer-equipped flask was charged with 300 g of hydroxyethylmethacrylate, 350 g of water, 350 g of methanol and 1.5 g ofazobisisobutylonitrile, which were stirred at room temperature for 60minutes. Then, the flask was thoroughly purged with a nitrogen gas, andthe resulting mixture was heated to 65° C. in the presence of nitrogengas flown slowly, and kept at this temperature for 3 hours forpolymerization. The resulting polymer was cooled to have a viscous,transparent liquid (BINDER B). The liquid prepared had a viscosity of1,800 mPa·s at 25° C., and the polymer in the mixed solvent ofwater/methanol had a number-average molecular weight of 150,000. Next,RECORDING MEDIUM 3 was prepared in the same manner as in RECORDINGMEDIUM PREPARATION EXAMPLE 1, except that polyvinyl alcohol was used asBINDER B obtained in the above procedure.

Recording Medium Preparation Example 4

An 85/15 by mass mixture of colloidal silica (Snowtex® C, NissanChemical) and polyvinyl alcohol (SMR-10HH®, Shin-Etsu Chemical) wasprepared, and incorporated with water to have a solid content of 20% bymass and stirred. It was spread on a PET film to 30 g/m² (dry basis),and dried at 110° C. for 10 minutes, to prepare RECORDING MEDIUM 4.

Ink Preparation Examples 1 to 5

Inks (INKS 1 to 5) each having a composition given in Table 1 wereprepared, where the components were thoroughly stirred to havesolutions, which were filtered under pressure by a filter (pore size:0.45 μm, Fluoroporefilter®, Sumitomo Electric). Copper phthalocyaninetetrasodium tetrasulfonate was supplied by Kishida Reagents Chemicals,gardenia yellow dye and capsicum dye and chlorophyll by Kiriya Chemical,and indigo carmine by Nacalai Tesque. TABLE 1 INK 1 INK 2 INK 3 INK 4INK 5 Copper 2.5 phthalocyanine tetrasodium tetrasulfonate Gardeniayellow dye 2.5 Capsicum dye 2.5 Chlorophyll 2.5 Indigo carmine 2.5Glycerin 7.5 7.5 7.5 7.5 7.5 Diethylene glycol 7.5 7.5 7.5 7.5 7.5*Acetylenol EH 0.1 0.1 0.1 0.1 0.1 Water 82.4 82.4 82.4 82.4 82.4(Unit: % by mass)*Acetylenol EH ®: Ethylene oxide adduct of acetylene alcohol (HLB = 14to 15, Kawaken Fine Chemicals)

Ink Preparation Example 6

A 500 mL Sakaguchi flask was charged with 100 mL of a malt/yeast extractYE culture medium [glucose: 1 mass %, yeast extract (Difco Laboratories,Inc.) 0.3 mass %, malt extract (Difco Laboratories, Inc.) 0.3 mass %,bacto peptone (Difco Laboratories, Inc.): 0.5 mass % and pure water:balance.] which was adjusted at a pH of 6.5. The medium was sterilizedat 120° C. for 20 minutes under pressure. It was cooled and inoculatedwith a loopful of monascus bacterium (Monascus purpureus, NBRC 4478)slant-cultured in a YM agar medium. The bacterium was cultured at 30° C.for 2 days while the medium was vibrated to prepare a seed bacteriumsolution. Then, 5 mL of the seed bacterium solution obtained wasinoculated in 100 mL of a YM medium, sterilized in the same manner, andcultured as a main culture for dye production at 30° C. for 3 days whilethe medium was vibrated. After the completion of the main culture, theculture solution was treated by a centrifugal separator (9,000 rpm) for10 minutes to be separated into a supernatant solution and a bacteriumbody. The supernatant solution, diluted 100 times with distilled water,had an absorbance of 0.2 at a wavelength of 500 nm. The supernatantsolution was mixed with the same volume of ethanol and stirred. Theresulting mixture was treated by a centrifugal separator (9,000 rpm) for10 minutes to separate a water-insoluble dye. The resulting supernatantsolution was concentrated and solidified to prepare a water-soluble reddye. Then, 10.0 parts of the dye was mixed with 90.0 parts of ethanol,thoroughly stirred to have a solution, which was filtered under pressureby a filter (pore size: 0.45 μm, Fluoroporefilter®, Sumitomo Electric)to prepare INK 6.

Culture Examples 1 to 4

In each of CULTURE EXAMPLES 1 to 4, a 5 L Shaking flask (Sakaguchiflask) was charged with 1 L of the same YM medium as used in INKPREPARATION EXAMPLE 6, and sterilized at 120° C. for 20 minutes underpressure, after it was adjusted at a pH of 6.5. It was cooled andinoculated with a loopful of monascus bacterium (Monascus purpureus,NBRC 4478) slant-cultured in a YM agar medium. The bacterium wascultured at 30° C. for 2 days while the medium was vibrated to prepare aseed bacterium solution.

On the other hand, 1 L glass jar was charged with 450 mL of the same YMmedium, which was sterilized at 120° C. for 20 minutes under pressure.It was cooled and inoculated with the above seed bacterium solution at10% by volume. Sulfuric acid, phosphoric acid and acetic acid were usedas pH adjustors for CULTURE EXAMPLES 1, 2 and 3, respectively. Theculture solution was stirred by aeration at 30° C. for 7 days while itwas kept at a pH of 4.0 after the culturing was started. CULTURE EXAMPLE4 adjusted the solution at a pH of 6.5 when the culturing was started,and then kept the pH level unadjusted. Production rate of monascorubrinin the culture solution prepared in each of CULTURE EXAMPLES 1 to 4 wasdetermined by HPLC in accordance with the procedure described in theInternational Publication 02/088265 pamphlet. The results are given inTable 2. TABLE 2 Monascorubrin Controlled pH production rate PH adjusterlevel (mg/L) CULTURE Sulfuric acid 4.0 220.5 EXAMPLE 1 CULTUREPhosphoric 4.0 259.6 EXAMPLE 2 acid CULTURE Acetic acid 4.0 953.5EXAMPLE 3 CULTURE No adjuster No adjuster 7.4 EXAMPLE 4 used used

As shown in Table 2, monascorubrin production rate was notably increasedwhen it was cultured in an acidic condition, and acetic acid as a pHadjuster produced monascorubrin in a still higher yield than a mineralacid of sulfuric or phosphoric acid. Rubropunctatin and monascorubrin,cultured by this method, gave a water-soluble dye more efficiently, whenthey were reacted by an amino compound by addition reaction.

Ink Preparation Example 7

The culture solution prepared in CULTURE EXAMPLE 3 was treated by acentrifugal separator (9,000 rpm) for 10 minutes to be separated into asupernatant solution and a bacterium body. The resulting dye-containingwet bacterium body, when freeze-dried, contained moisture at 75.6% bymass.

Then, 400 g of the resulting wet bacterium body was incorporated with 10L of ethyl acetate and stirred for 1 hour. The mixture was filtered by afilter paper to be separated into a filtrate and a bacterium body. Thefiltrate was treated to separate the ethyl acetate layer from theaqueous layer. The ethyl acetate extract solution was washed with thesame volume of water twice. The washed ethyl acetate extract solutionwas concentrated and solidified to prepare a reddish orange dyecontaining monascorubrin and rubropunctatin.

Next, 10.8 g of the reddish orange dye was incorporated withacetonitrile to prepare 2095 mL of the acetonitrile solution containingthe reddish orange dye. It was reacted with the same volume of a 30mg/mL aqueous monosodium glutamate solution at room temperature for 3days with stirring, and the product was concentrated and solidified toprepare a water-soluble dye. The dye was mixed with glycerin, diethyleneglycol, acetylenol and water with sufficiently stirring to prepare a 2.5(dye)/7.5/7.5/0.1/82.4 by mass solution. The resulting solution wasfiltered under pressure by a filter (pore size: 0.45 μm,Fluoroporefilter®, Sumitomo Electric) to prepare INK 7.

On completion of the reaction with monosodium glutamate to prepare thewater-soluble dye, the reaction solution was analyzed by reverse-phaseHPLC, which detected neither monascorubrin nor rubropunctatin. Moreover,the reaction solution, diluted 100 times with distilled water, wasanalyzed for absorbance at 500 nm. It was 0.68.

Printed Matter Preparation Examples 1 to 10

Each of RECORDING MEDIA 1 to 4 was solid-printed with one of INKS 1 to 7by an on-demand ink jet printer (PIXUS iP3100, Canon) with a heatingelement as an ink ejecting energy source to prepare PRINTED MATTERS 1 to10. Table 3 describes these printed matters. TABLE 3 Base INK PRINTERMATTER 1 1 1 PRINTER MATTER 2 2 1 PRINTER MATTER 3 3 1 PRINTER MATTER 44 1 PRINTER MATTER 5 1 2 PRINTER MATTER 6 1 3 PRINTER MATTER 7 1 4PRINTER MATTER 8 1 5 PRINTER MATTER 9 1 6 PRINTER MATTER 10 1 7

<Evaluation of Color Erasion/Reduction Capacity>

Examples 1 to 10

Color erasion/reduction capacity was tested using a remote plasma deviceshown in FIG. 1, which had the following characteristics; size of thedischarge electrode 41 and counter electrode 42, both of nickel: 225 by100 by 1 mm (thickness); distance between the electrodes: 5 mm; lengthof needles on the discharge electrode 41: 1 mm; and needle density: 144needles/cm². Each of PRINTED MATTERS 1 to 10 was discharge-treated whileit was transferred at 60 cm/minute in the closed remote plasma device,where a DC voltage of −3 kV was applied to the discharge electrode 41and air was introduced at 1.2 m/second (EXAMPLES 1 to 10). The remoteplasma device 4 and the plate 53 were arranged to have a distance of 10mm between the center of the plane from which an oxidative gas wasemitted in the remote plasma device and the printed matter.Concentration of ozone on the plane from which the oxidative gas wasemitted was measured by an ozone concentration meter (Model 1300, TokyoDylec). It was about 100 ppm.

Optical density of each of PRINTED MATTERS 1 to 10 was measured by acolor transmission/reflection concentration meter (X-Rite310TR®, X-RiteInc.) before and after the discharge treatment. Ratio of the opticaldensity after the discharge treatment to that before the treatment isdefined as residual optical density rate, which was determined by thefollowing formula:Residual optical density rate=(Optical density after the dischargetreatment/Optical density before the discharge treatment)×100.The results are given in Table 4.

Example 11

PRINTED MATTER 10 was discharge-treated in the same manner as in EXAMPLE1 using the same remote plasma device, except that a DC voltage of −4 kVwas applied to the discharge electrode, and its residual optical densityrate was determined. The result is given in Table 4. Concentration ofozone on the plane from which the oxidative gas was emitted was about140 ppm, as measured by an ozone concentration meter (Model 1300, TokyoDylec).

Examples 12 to 21

Color erasion/reduction capacity was tested using a remote plasma deviceshown in FIG. 2B, which had the following characteristics; size of thedielectric 43 of alumina ceramic having an elliptical cross-section: 250mm in diameter (major axis) by 30 mm in diameter (minor axis) by 70 mmin length and 1 mm in thickness; the counter electrode 42 embedded inthe dielectric was made of tungsten; the discharge electrode 41 was madeof tungsten having an outer diameter of 0.4 mm; and distance between theelectrodes: 0.5 mm. Each of PRINTED MATTERS 1 to 10 wasdischarge-treated while it was transferred at 150 cm/minute in theclosed remote plasma device, where a voltage of 3 kV as Vpp having asquare waveform and frequency of 15 kHz was applied and air wasintroduced at 2 m/second. The residual optical density rate wasdetermined in the same manner as in EXAMPLE 1 (EXAMPLES 12 to 21). Theresults are given in Table 5. The remote plasma device 4 and the plate53 were arranged to have a distance of 30 mm between the center of theplane from which the oxidative gas was emitted in the remote plasmadevice and the printed matter. Concentration of ozone on the plane fromwhich the oxidative gas was emitted was about 200 ppm, as measured by anozone concentration meter (Model 1300, Tokyo Dylec).

Comparative Example 1

Light recycled paper (Fuji Xerox) was solid-printed with INK 7 by anon-demand ink jet printer (PIXUS iP3100, Canon) with a heating elementas an ink jetting energy source to prepare PRINTED MATTER 12. It wasdischarge-treated in the same manner as in EXAMPLE 1 using the samedevice to determine its residual optical density rate. The result isgiven in Table 5.

Comparative Example 2

PRINTED MATTER 10 was placed 25 cm under a daylight color fluorescentlamp and irradiated with light (2000 lux) for 20 hours to determine itsresidual optical density rate. The result is given in Table 5. TABLE 4Residual optical Recording density rate medium Dye in ink (%) EXAMPLEAlumina-coated Copper 77 1 paper phthalocyanine tetrasodiumtetrasulfonate EXAMPLE Alumina-coated Copper 59 2 paper phthalocyaninetetrasodium tetrasulfonate EXAMPLE Alumina-coated Copper 56 3 paperphthalocyanine tetrasodium tetrasulfonate EXAMPLE Silica-coated Copper47 4 paper phthalocyanine tetrasodium tetrasulfonate EXAMPLEAlumina-coated Gardenia yellow 10 5 paper dye EXAMPLE Alumina-coatedCapsicum dye 16 6 paper EXAMPLE Alumina-coated Chlorophyll 41 7 paperEXAMPLE Alumina-coated Indigo carmine 14 8 paper EXAMPLE Alumina-coatedMonascus dye 10 9 paper EXAMPLE Alumina-coated Monascus dye 12 10 paperEXAMPLE Alumina-coated Monascus dye 9 11 paper

TABLE 5 Residual optical Recording density rate medium Dye in ink (%)EXAMPLE 12 Alumina- Copper 75 coated paper phthalocyanine tetrasodiumtetrasulfonate EXAMPLE 13 Alumina- Copper 51 coated paper phthalocyaninetetrasodium tetrasulfonate EXAMPLE 14 Alumina- Copper 50 coated paperphthalocyanine tetrasodium tetrasulfonate EXAMPLE 15 Silica- Copper 42coated paper phthalocyanine tetrasodium tetrasulfonate EXAMPLE 16Alumina- Gardenia yellow 8 coated paper dye EXAMPLE 17 Alumina- Capsicumdye 13 coated paper EXAMPLE 18 Alumina- Chlorophyll 36 coated paperEXAMPLE 19 Alumina- Indigo carmine 9 coated paper EXAMPLE 20 Alumina-Monascus dye 6 coated paper EXAMPLE 21 Alumina- Monascus dye 7 coatedpaper COMPARATIVE Common paper Monascus dye 99 EXAMPLE 1 COMPARATIVECommon paper Monascus dye 20 EXAMPLE 2

These results clearly indicate that EXAMPLES 1 to 21 reduced residualoptical density rates to a low level, demonstrating excellent colorerasion/reduction capacity of each printed matter printed with an inkjet ink with images formed on the recording medium coated with theinorganic pigment, because it was exposed to an oxidative gas generatedby the remote plasma device. The capacity is particularly noted when themonascus dye, gardenia yellow dye, capsicum dye and indigo dye are used.It is also noted that the recording medium coated with alumina as aninorganic pigment gives higher color erasion/reduction capacity.

Recording Medium Preparation Examples 5 to 8

A mixture of fine colloidal silica powder and polyvinyl alcohol(SMR-10HH®, Shin-Etsu Chemical) with a ratio of 85/15 by weight wasprepared, and incorporated with water to have a solid content of 20% bymass and stirred. It was spread on a common paper (A4 size) to 35 g/m²(dry basis), and dried at 110° C. for 10 minutes, to prepare RECORDINGMEDIA 5 to 8. The inorganic powder on each of the recording media wasanalyzed for its pore volume and dispersed particle diameter by theprocedure described above. The results are given in Table 6. TABLE 6Pore volume of silica Dispersed silica powder [cc/g] particle diameter[μm] Recording 0.2 0.9 medium 5 Recording 0.3 0.6 medium 6 Recording 0.40.3 medium 7 Recording 0.5 0.2 medium 8

Recording Medium Preparation Examples 9 to 13

A mixture of fine alumina powder of varying type and polyvinyl alcohol(SMR-10HH®, Shin-Etsu Chemical) with a ratio of 85/15 by weight wasprepared, and incorporated with water to have a solid content of 20% bymass and stirred. Each was spread on a common paper (A4 size) to 30 g/m²(dry basis), and dried at 110° C. for 10 minutes, to prepare RECORDINGMEDIA 9 to 13. The inorganic powder on each of the recording media wasanalyzed for its pore volume and dispersed particle diameter by theprocedure described above. The results are given in Table 7. TABLE 7Pore volume of silica Dispersed silica powder [cc/g] particle diameter[μm] Recording 0.2 0.8 medium 9 Recording 0.4 0.7 medium 10 Recording0.6 0.2 medium 11 Recording 0.7 0.1 medium 12 Recording 0.9 0.08 medium13

Ink Preparation Examples 8 to 10

Inks each having a composition given in Table 8 were prepared, where thecomponents were thoroughly stirred to have solutions, which werefiltered under pressure by a filter (pore size: 0.45 μm,Fluoroporefilter®, Sumitomo Electric). Gardenia yellow and capsicum dyeswere supplied by Kiriya Chemical, and copper phthalocyanine tetrasodiumtetrasulfonate by Kishida Reagents Chemicals. TABLE 8 INK 8 INK 9 INK 10Gardenia blue dye 2.5 — — Capsicum dye — 2.5 — Copper phthalocyanine — —2.5 tetrasodium tetrasulfonate Glycerin 7.5 7.5 7.5 Diethylene glycol7.5 7.5 7.5 Acetylenol EH 0.1 0.1 0.1 Water 82.4 82.4 82.4

Printed Matter Preparation Examples 13 to 24

Each of RECORDING MEDIA 5 to 8 was solid-printed with one of INKS 8 to10 in the same manner as in PRINTED MATTER PREPARATION EXAMPLES 1 to 10to prepare PRINTED MATTERS 13 to 24. Dye ionization potential wasdetermined for the solid dye before it was used for printing and the dyeon a printed matter by an aerial photoelectron spectrometer (e.g., AC-1,Riken Keiki), where the sample was irradiated with light having anintensity of 10 nW (5.9 eV energy) or more. The results are given inTable 9.

Printed Matter Preparation Examples 25 to 34

Each of RECORDING MEDIA 9 to 13 was solid-printed with INK 5 or 6 in thesame manner as in PRINTED MATTER PREPARATION EXAMPLES 1 to 10 to preparePRINTED MATTERS 25 to 34. Dye ionization potential was determined foreach of these printed matters. The results are given in Table 10.

<Evaluation of Color Reduction/Erasion Capacity>

Examples 22 to 33

Color reduction/erasion capacity was tested using a remote plasma deviceshown in FIG. 3, which had the following characteristics; size of theplate-shape dielectric 43 made of alumina ceramic: 225 by 60 by 1 mm(thickness); the discharge electrode 41 and the counter electrode 42,both made of tungsten and embedded in the dielectric: 0.15 mm in outerdiameter; and distance between the electrodes: 1.5 mm. The cover 44 wasmade of a 2 mm thick acrylic plate, and distance between the cover 44and the plate-shape dielectric 43 was 2 mm. Each of PRINTED MATTERS 13to 24 was discharge-treated while it was transferred at 120 cm/minute inthe closed remote plasma device, where an AC voltage of 4 kV as Vpphaving a triangular waveform and frequency of 10 kHz was applied to thedischarge electrode and air was introduced at 1.8 m/second in EXAMPLES22 to 33. The remote plasma device 4 and the belt 51 were arranged tohave a distance of 20 mm between the center of the plane from which anoxidative gas was emitted in the remote plasma device and the printedmatter. Concentration of ozone on the plane from which the oxidative gaswas emitted was about 160 ppm, as measured by an ozone concentrationmeter (Model 1300, Tokyo Dylec).

The residual optical density rate was measured in the same manner as inEXAMPLE 1. The results are given in Table 9.

Examples 34 to 43

Color reduction/erasion capacity was tested using a remote plasma deviceshown in FIG. 4, which had the following characteristics; size of thedielectric 43 made of single-crystal magnesia: 250 by 60 by 0.5 mm(thickness); size of the discharge electrode 41 of chromium provided onthe dielectric 43: 225 by 50 by 1 mm (thickness); size of the counterelectrode 42 of stainless steel plate: 225 by 50 by 1 mm (thickness);and distance between the dielectric 43 and the counter electrode 42: 2mm. Each of PRINTED MATTERS 13 to 24 was achromatization-treated in theclosed system (EXAMPLES 34 to 43), where the AC power source shown inFIG. 5 was used and the aerial gap had a structure shown in FIG. 7. Theelectric elements 72, 73, 74 and 75 were of 100 kΩ, 10 kΩ, 1000 pF and10 kΩ. Distance between the metallic electrodes in the aerial gap 8 wasset at 2 mm. Each printed matter was discharge-treated while it wastransferred at 180 cm/minute and air was introduced at 1.5 m/second,where an AC voltage (100 V, 50 Hz) was applied to an inverter neontransformer (M-5, RECIP CORP.) to apply an AC voltage (34 kV as Vpp and50 Hz) including a pulsed waveform to the discharge electrode. Theremote plasma device 4 and the belt 51 were arranged to have a distanceof 25 mm between the center of the plane from which an oxidative gas wasemitted in the remote plasma device 4 and the printed matter.Concentration of ozone on the plane from which the oxidative gas wasemitted was about 200 ppm, as measured by an ozone concentration meter(Model 1300, Tokyo Dylec).

The residual optical density rate was measured in the same manner as inEXAMPLE 1. The results are given in TABLE 10 Table 9 Ionizationpotential Ionization Residual of dye potential optical Recording powderof image density medium Dye in ink (eV) (eV) rate (%) EXAMPLE RECORDINGGardenia blue 5.3 5.2 20 22 MEDIUM 5 dye EXAMPLE RECORDING Gardenia blue5.3 5.17 17 23 MEDIUM 6 dye EXAMPLE RECORDING Gardenia blue 5.3 5.1 1324 MEDIUM 7 dye EXAMPLE RECORDING Gardenia blue 5.3 5.05 10 25 MEDIUM 8dye EXAMPLE RECORDING Capsicum dye 5.95 5.85 16 26 MEDIUM 5 EXAMPLERECORDING Capsicum dye 5.95 5.79 13 27 MEDIUM 6 EXAMPLE RECORDINGCapsicum dye 5.95 5.7 11 28 MEDIUM 7 EXAMPLE RECORDING Capsicum dye 5.955.65 9 29 MEDIUM 8 EXAMPLE RECORDING Copper 6.05 6.02 76 30 MEDIUM 5phthalocyanine tetrasodium tetrasulfonate EXAMPLE RECORDING Copper 6.056.0 65 31 MEDIUM 6 phthalocyanine tetrasodium tetrasulfonate EXAMPLERECORDING Copper 6.05 5.98 59 32 MEDIUM 7 phthalocyanine tetrasodiumtetrasulfonate EXAMPLE RECORDING Copper 6.05 5.95 55 33 MEDIUM 8phthalocyanine tetrasodium tetrasulfonate

TABLE 10 Ionization potential Ionization Residual of dye potentialoptical Recording Dye in powder of image density medium ink (eV) (eV)rate (%) EXAMPLE RECORDING Monascus 5.45 5.35 16 34 MEDIUM 9 dye EXAMPLERECORDING Monascus 5.45 5.31 13 35 MEDIUM 10 dye EXAMPLE RECORDINGMonascus 5.45 5.28 10 36 MEDIUM 11 dye EXAMPLE RECORDING Monascus 5.455.24 8 37 MEDIUM 12 dye EXAMPLE RECORDING Monascus 5.45 5.21 6 38 MEDIUM13 dye EXAMPLE RECORDING Indigo 5.85 5.71 22 39 MEDIUM 9 carmine EXAMPLERECORDING Indigo 5.85 5.56 16 40 MEDIUM 10 carmine EXAMPLE RECORDINGIndigo 5.85 5.5 11 41 MEDIUM 11 carmine EXAMPLE RECORDING Indigo 5.855.38 9 42 MEDIUM 12 carmine EXAMPLE RECORDING Indigo 5.85 5.33 7 43MEDIUM 13 carmine

The above results were with the dyes having an ionization potential of6.0 eV or less in the powder state. As shown, the ink exhibits excellentcolor erasion/reduction capacity when the dye in the ink fixed on therecording medium has an ionization potential lower than that of thesolid (powder) ink by 0.1 eV or more. It is also shown that a monascus,gardenia and capsicum dyes give an ink of excellent colorerasion/reduction capacity.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2005-289107, filed Sep. 30, 2005, which is hereby incorporated byreference herein in its entirety.

1. An achromatizing method for achromatizing a dye on a printed matter,comprising exposing the dye to an oxidative gas generated by using aremote plasma device.
 2. The achromatizing method according to claim 1,wherein the remote plasma device produces the oxidative gas by coronadischarge, creeping discharge or dielectric barrier discharge asdischarging means, and a printed surface of the printed matter is spacedfrom a plane from which the oxidative gas generated by the remote plasmadevice is emitted by more than 0 mm and 100 mm or less.
 3. Theachromatizing method according to claim 1, wherein the printed matter isstationary or moving at a relative velocity of 2000 cm/minute or less tothe plane from which the oxidative gas is emitted in the remote plasmadevice.
 4. The achromatizing method according to claim 1, wherein theprinted matter is produced by applying a dye-containing ink to arecording medium to form a colored portion thereon, and the recordingmedium contains a porous inorganic pigment in its surface.
 5. Theachromatizing method according to claim 1, wherein the dye has a polyenestructure.
 6. The achromatizing method according to claim 4, wherein theink is applied to the recording medium by an ink jet recording method.7. An achromatization device for achromatizing a dye on a printedmatter, comprising a remote plasma device having means which produces anoxidative gas by any discharging means of corona discharge, creepingdischarge and dielectric barrier discharge, and supporting means forpositioning the printed matter in such a way that the dye thereon isable to be exposed to the oxidative gas.
 8. The achromatization deviceaccording to claim 7, wherein the supporting means further includesmeans for transferring the printed matter into or out of theoxidative-gas applied region in which the oxidative gas generated by theremote plasma device is applied to the printed matter.
 9. A method forrecycling a recording medium, comprising a step for achromatizing acolored portion on a printed matter by the method for achromatizing adye according to claim 1.